Method and means for the examination of jewels



Jan. 21, 1930. H. MICHEL ET AL METHOD AND MEANS FOR THE EXAMINATION OF JEWELS Filed Feb. 19. 1926 2 Sheets-Sheet 1 Jig 1,

ATTORNEYS Jan. 21, 1930. H. MICHEL ET AL METHOD AND MEANS FOR THE EXAMINATION OF JEWELS BY Qusfav 7624/ PM 1- 3%- M .W

ATTORNEYS Patented Jan. 21 1030 tals, jewels,

UNITED STATES PATEN orrce HERMANN MICHEL AN!) GUSTAV RIEDL, O F VIENNA, AUSTRIA, ASSIGNORS OF ONE-- TRIED TO GUSTAVE Ii. HERZ, OF NEW YORK, N. Y.

METHOD AND MEANS'FOR THE EXAMTNATION OF. JEWELS Application filed February 19, 1926, Serial No. 89,286, and in Austria February 21, 1925.

The object of this invention is a method of and apparatus for utilizing the optical prop erties of coloured substances, minerals, crysetc., to distinguish between valuable coloured jewels and others of the same colour but of a different less valuable kind;

also between tions. volved genuine jewels and their imita- The following is the principle in- The mineral is put in such a position that pear in the identical colour when the rays coloured by one colour filter pass through these two substances, but appear in two different colours when subjected to the rays coloured by another colour filter and can thereby be distinguished from one another. By arranging the colour filters in such a way that they can be easily changed, it is possi le to distinguish between translucent or transparent materials, having difierent absorption characteristics for coloured light rays, also between the genuine minerals and imitations of the same colour, as also between objects of difierent luminescence.

The colour filters are selected from the following viewpoints:

-The characteristics 'of the variousl col- 'oured minerals with res ect to light a sorpgenuine emerald, a blue-green turmalin and a green glass. Read on the scale of a pocket spectroscope, the approximate figures of the wave lengths are as follows:

The emerald shows weak red light between 700045100 A (i=1 Augstroem-unit). The yellow rays are nearly totally absorbed between. 6100 A and 5750 A. The green tints hilated;

are more intense between 5750 A and 5000 A. The blue tints are very much weaker between 5000 A and 47 50 A, but still clearly distinguishable.

The blue-green turmalineshows the "red part of the spectrum totally annihilated upi to 6500 A. From 6500 A downwards all colour tints of the spectrum'can be observed.

The green glass shows weak red tints from 6300 A-6000 A, and intense yellow and green tints from 6000-5100 A, and blue tints from 5000 A-4600 A.

The filter No. 1 now only permits red light of the wave lengths of 7500-6650 A to pass through and annihilate the tints between 6650 A and 5100. A, and permits blue tints between 5100 A and 4250 A to pass through.

' I Filter 0. 2 permits red rays from 7600 A- 6700 A to pass through; tints between 6700- 5900 A are annihilated. The green tints between 5900 and 5400 A pass through more intensely than the green tints from 5400 A and'5000 A which are very much weakened. The tintsbelow 5000 A By combining these two filters, the emerald therefore appears in a peculiar red tint on filter 1 and 2, whereas the turmalin and the glass appear blue on filter 1 and green on filter 2.

We have also combined a dichroscope with our instrument for the following reasons:

The colour of a mineral is due to the absorption of certain portions of white light in'its passage through themineral. This is known as selective absorption. The remainder of the white light, namely that which is not absorbed in the mineral, blends to produce the colour seen. In anisotropic substances .the remaining colour is depending upon the sense of undulation. In the dichroscope the colors are seen side by side and very slight variations in tints are thus easily recognized. By observing minerals illuminated by filtered light, through the dichroscope,

are practically anm 1y be reco ed.

The ob]ects and advantages of the invendistinguishing characteristics may more easition will be better understood by reference to the accompanyin drawing in which Fig. 1 is a vertica section through the apparatus;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a vertical section through a modified apparatus; and I Fig. 4 is a view of the lower end of the dichroscope shown in Fi 3.

In Figure 1 A is a wooden case, on the bottom of which an incandescent lamp (B) has been fastened. A lens (0) collects the rays emanatin from this lamp and throws them throu h t e colour filter (F), to the 'ewels (J) p aced on a stationary glass disk S is a shield protecting the eye from outside light.

The colour filters F, F F F set into a metal disk (H) which revolves around an axis (X) as shown in Figure 2.

Figure 3 shows the instrument with the dichroscope attached. K is the dichroscope, consisting of a refractirif rhombohedren of calcite or Iceland spar mounted in a cylindrical case. At the lower end is a small rectangular opening (0) and at the other end an eyepiece (N) i In using the apparatus a mineral to be tested is mounted uponthe support therefor. The proper filter is then interposed between the source of light and the mineral. The effeet is noted and another selected filter is interposed. The observation is repeated and the results are compared with similar observations of a standard mineral, that is, one of known quality.

Various changes may be'made in the details of the operation as well as in the apparatus employed without departing from the invention-or'sacrificing any of the advanta es thereof.

hat we claim as our invention is 1. In an apparatus-for examinin transparent and translucent substances, t e comination of a source of light, means for projecting a beam therefrom, a support for the substance to be' examined in the path of the beam, a rotatable table having a plurality of 1i ht filters thereon adapted to be dispose between the support and the beam projecting means and a dichroscope above the support.

2. The method of establishing the identity of colored transparent and translucent minerals which comprises subjectin the mineral to a beam of light, successivsy filtering selected portions of the spectrum from the beam before it passes through the mineral so thatthe mineral appearsin a different color, observing the efiect of each of the filtered lights passing through the mineral and comparing the observations with the previously ascertained eflect upon minerals of known identity.

In testimony whereof we afiix our signatures.

HERMANN MICHEL.- GUSTAV RIEDL.

CERTIFICATE OF. CORRECTION Patent No. 1,744,485. Granted January 211, 1930, m

HERMANN MICHEL ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 25, for the word "materials" read "minerals"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of March, A; D. 1930.

v M. J. Moore,

- (Seal) Acting Commissioner of Patents. 

